1. Field of the Invention
This invention relates to a sun tracker and more particularly to a tracker for sensing the position of a solar tracking device with respect to the sun in order to effect movement of the device as the sun moves.
2. Description of the Prior Art
Commonly owned U.S. Pat. No. 4,205,659 discloses a solar energy collector or concentrator having a paraboloid-shaped reflector, an elongate heat receiving member or pipe at the focus of the reflector and one or more photoelectric sensors in the bottom of the reflector. The photoelectric sensors are positioned such that when the sun moves westward of alignment with the paraboloid shaped reflector, the sensors are excited and actuate a motor to move the reflector into alignment with the sun. Although such device is effective during sunny or partially clouded days, it has limited ability to pick up the sun after the sun has been obscured by clouds for several hours because the location of the photoelectric sensors in the bottom of the reflector subjects the sensors to shading by the lateral walls of the reflector.
U.S. Pat. No. 4,153,039 discloses a photosensor which is located in the bottom of a trough shaped mirror which renders it incapable of picking up the sun when the sun is at a substantial angle from alignment with the mirror.
U.S. Pat. No. 4,068,653 discloses a solar heating unit having photocells which are mounted at the end of long tubes in order to shade them so that they will only respond to substantially direct light rays. Accordingly the photocells in the patented structure respond only to sunlight which is substantially aligned with the curved reflector.
U.S. Pat. No. 4,098,264 discloses a tracking solar collector wherein two photocells are mounted in the bottom of a cylindrical housing which has two compartments formed by an opaque wall extending diametrically within the housing. The sensor forms a collimator which responds to energy from the sun only if it is almost precisely aligned with the collector.